Server affinity. If your application is to be deployed into a clustered environment,then your clients will suffer from server affinity. This occurs because a user’s session is unique to each server, so if a user connects to another server, he will receive a wholenew session. Server affinity prevents failover (http://en.wikipedia.org/wiki/Failover), thus reducing your ability to load balance within a cluster. 1)There are solutions for session replication in clustered environment, but they are typically very expensive and complex, and they always incur some performance overhead.